High heat resistant steels



United States Patent 1 Claim. 01. 75126) This application is a continuation of my pending ap plication, Serial No. 686,556, filed September 27, 1957, now abandoned.

The present invention relates to alloy steels with a high resistance. In particular it is directed to alloy steel intended preferably for use in the production of tools with very severe requirements for high heat resistance.

The tools aforesaid are forging tools, hot-pressing tools, die-casting tools, and extrusion tools. Certain of those tools can attain temperatures of between 900 and 1000 C. when in use. As it is not possible for these tools to hold the said temperatures, they must be cooled down discontinuously with water, or in some other way, to temperatures of approximately 500. The said cooling takes place very rapidly, and therefore the requirements stipulated for the alloy used are very severe.

Hitherto, alloys of, e.g. the following compositions have been used:

The hot hardness of the above-mentioned steels has been determined with the aid of a Vickers diamond at the temperatures 600, 650, 700 and 750 C. All of the test pieces of the alloys have been hardened and tempered at 600 C. before the hardness testing. A summary of the hardness values is given in the following table:

HOT HARDNESS D.P.![-I.

Steel N0 600 C. 650 C. 700 C. 750 C.

I 290 187 113 70 II 272 197 127 75 III .1 235 103 105 62 IV 312 205 108 67 V 276 232 180 137 The heat resistance of the above-mentioned alloys is determined by the alloy elements, of which different alloys have different properties that raise the heat resistance. As a rule, the greater the content of the alloying element, the greater heat resistance is obtained. Most alloys, however, have the disadvantage that the greater the quantity of alloying element used, the poorer the heat-conducting properties of the alloy. The poorer the heat-conducting properties, the greater the risk for cracking on rapid cooling of a tool made of the alloy.

Of the above-mentioned five alloys, it has proved that all of them are sensitive to cracking when cooled, but to different degrees. Thus, steel V is the one most sensitive to heat checking; thereafter in the order mentioned: steels I, IV, II and III.

The above-mentioned known steels can also contain 3,272,622 Patented Sept. 13, 1966 quantities of one or more of the alloys titanium, columbium and tantalum, with contents of up to 0.5%.

In the above-mentioned alloys it is known to vary the relation between the alloys contained in them, so that alloys with greater heat-resistance-raising properties dominate the alloy, a high heat resistance thus being obtained with as small a quantity of alloying elements as possible, in order to obtain high heat resistance, at the same time as good heat-conducting properties are obtained.

It is one of the principal objects of the present invention to provide a new alloy of the last-mentioned kind, i.e., with a low content of alloying elements and high heat resistance. A further object is to provide novel articles, such as tools, etc., made from such novel steel.

The steel of this invention is characterized by its containing, 0.20-0.40% carbon; 0.20.5% of silicon; 2-3% of chromium; 2-3% of molybdenum; 03-06% of vanadium; and 2-3 of cobalt; and in addition, normal con-' A steel alloy is made according to this invention which has the following composition (in percent by weight) of alloying elements:

ANALYSIS 0 Si Cr Mo The steel has the following hot hardness:

Steel No. 600 0. Hot hardness, D.P.1-I. at 750 0.

VI "I 350 225 This steel has proved to be superior to all hitherto known steels tested for which high heat resistance requirements are severe; and which at the same time must be capable of withstanding sudden cooling.

Example 2 A steel is made in accordance with this invention which has the following composition:

Percent It will be understood that the foregoing description of the invention and the example set forth are merely illustrative of the principles thereof. Accordingly the appended claim is to be construed as defining the invention within the full spirit and scope thereof.

What is claimed is:

An alloy steel with a high heat resistance characterized by the feature that it consists essentially of: 0.28-0.32% carbon, 0.20-0.35% Si, 2.63.0% Cr, 2.63.0% Mo,

References Cited by the Examiner UNITED STATES PATENTS 1,496,980 6/1924 Armstrong 75l28 X 1,545,094 7/1925 Giles 75-128 X 2,289,449 7/1942 Nelson 75l26 4 FOREIGN PATENTS 377,011 7/1932 Great Britain. 404,565 1/1934 Great Britain.

5 DAVID L. RECK, Primary Examiner.

P. WEINSTEIN, Assistant Examiner. 

